Climate change alters elevational phenology patterns of the European spruce bark beetle (Ips typographus)

Abstract

The European spruce bark beetle Ips typographus is the most important insect pest in Central European forests. Under climate change, its phenology is presumed to be changing and mass infestations becoming more likely. While several studies have investigated climate effects across a latitudinal gradient, it remains an open question how phenology will change depending on elevation and topology. Knowing how an altered climate is likely to affect bark beetle populations, particularly across diverse topographies and elevations, is essential for adaptive management. We developed a time-varying distributed delay model to predict the phenology of I. typographus. This approach has the particular advantage of capturing the variability within populations and thus representing its stage structure at any time. The model is applied for three regional climate change scenarios, A1B, A2 and RCP3PD, to the diverse topography of Switzerland, covering a large range of elevations, aspects and slopes. We found a strong negative relationship between voltinism and elevation. Under climate change, the model predicts an increasing number of generations over the whole elevational gradient, which will be more pronounced at low elevations. In contrast, the pre-shift in spring swarming is expected to be greater at higher elevations. In comparison, the general trend of faster beetle development on steep southern slopes is only of minor importance. Overall, the maximum elevation allowing a complete yearly generation will move upwards. Generally, the predicted increase in number of generations, earlier spring swarming, more aggregated swarming, together with a projected increase in drought and storm events, will result in a higher risk of mass infestations. This will increase the pressure on spruce stands particularly in the lowlands and require intensified management efforts. It calls for adapted long-term silvicultural strategies to mitigate the loss of ecosystem services such as timber production protection against rockfall and avalanches and carbon storage. K E Y W O R D Sforest pest, infestation risk, Norway spruce (Picea abies), phenology, temperature, timevarying distributed delay model, voltinism

Białowieża Forest—A Relic of the High Naturalness of European Forests

“…The course and dynamics of ecological processes are very important in the light of the recent climate change, as they adjust ecosystems to new conditions by changing species abundance and distribution in space, which leads to a reassembling of species communities and networks of interactions between species. On the other hand, climate warming brings modification of the course, frequency and intensity of natural processes, leading to their increase [107] or decline [108], which influences the rules of ecosystem assembly.…”

Do bark beetle outbreaks amplify or dampen future bark beetle disturbances in Central Europe?

“…In the temperate and boreal biome, bark beetles are the most important insect disturbance agents (Netherer & Schopf, 2010; Raffa, Grégoire, & Lindgren, 2015). Bark beetle outbreaks are particularly affected by climate change due to the ectothermic physiology of the beetles (Jakoby, Lischke, & Wermelinger, 2019) and the drought sensitivity of the defence system of trees (Huang et al., 2020). Consequently, bark beetle outbreaks are intensifying in many forests globally (Hicke, Meddens, & Kolden, 2016; Marini et al., 2017).…”

Seasonality, niche management, and vertical migration in landscapes of relief

“…The advantages of such a buffer may be stymied by more spatio-temporally uniform plant phenological dynamics. A similar pattern is expected for bark beetles (Ips typographus), as the timing of diapause termination and swarming is expected to shift more rapidly at high elevations and on south-facing slopes in the Alps (Jakoby et al 2019). Adjustments to the historic elevational trend in insect swarming phenology may impact insectivorous altitudinal migrants that live there (e.g.…”